Diminution (Part II)
Here is the same tune with the various linear units slurred and marked. If you pick one note from each diminution you will find the outline of the well-known tune being varied. (if you can't work it out, click here)

One of the reasons for doing a Schenkerian analysis is to discover the simple progressions that lie behind apparently complicated music. A variation is an obvious example of composers working in this way - the simple theme underpins the figurations of the variation.

As you will find out in How to do a Schenkerian Analysis, the next stage of an analysis is to decide which note from each linear unit is the one being prolonged.
You may ask "Why bother?", but this is in fact where Schenkerian analysis starts to become really interesting. Click on the example to find out.